decouple eth2 from store and lighthouse_network (#6680)

- #6452 (partially)


  Remove dependencies on `store` and `lighthouse_network`  from `eth2`. This was achieved as follows:

- depend on `enr` and `multiaddr` directly instead of using `lighthouse_network`'s reexports.
- make `lighthouse_network` responsible for converting between API and internal types.
- in two cases, remove complex internal types and use the generic `serde_json::Value` instead - this is not ideal, but should be fine for now, as this affects two internal non-spec endpoints which are meant for debugging, unstable, and subject to change without notice anyway. Inspired by #6679. The alternative is to move all relevant types to `eth2` or `types` instead - what do you think?

beacon_node/http_api/Cargo.toml

@@ -50,7 +50,6 @@ warp_utils = { workspace = true }
 [dev-dependencies]
 genesis = { workspace = true }
 proto_array = { workspace = true }
-serde_json = { workspace = true }
 
 [[test]]
 name = "bn_http_api_tests"